====== 4.5 Trust Server ======

Central trust server for certificate validation.

===== Concept: Single Point of Trust =====

  * All clients query the Trust Server
  * Trust Server decides on trustworthiness
  * Central control over certificate status
  * Real-time revocation possible

===== Architecture =====

<code>
[Client] -> [Proxy] -> [Trust Server]
                          |
                    [Certificate DB]
</code>

===== API Endpoints =====

^ Endpoint ^ Function ^
| POST /validate | Verify certificate |
| GET /trusted | List of trusted certs |
| POST /revoke | Revoke certificate |

===== Configuration in Proxy =====

<code javascript>
{
  "TrustServer": {
    "Url": "https://trust.intern",
    "ApiKey": "...",
    "CacheSeconds": 60,
    "FailOpen": false
  }
}
</code>

===== Fail-Closed =====

With ''FailOpen: false'':
  * Trust Server not reachable -> Access denied
  * Maximum security
  * Availability of Trust Server critical

===== High Availability =====

  * Run Trust Server in cluster
  * Load balancer in front
  * Local cache for short-term outages